Electrodes of traditional twisted nematic type liquid crystal display (TN LCD) are separately formed on two substrates, whose liquid crystal molecules rotate in the plane orthogonal to the substrates, with high transmittance, low power consumption and simple manufacturing process. However, the viewing angle is narrower as the orientations of liquid crystals adjacent to surfaces of the two substrates are orthogonal with each other. In order to realize wide viewing angle, there exist a Fringe Field Switching (FFS) type liquid crystal display employing a fringe field and an In Plane Switching (IPS) type liquid crystal display employing a horizontal electric field, and electrodes of the FFS type liquid crystal display and the IPS type liquid crystal display are both formed on the same substrate, whose liquid crystal molecules rotate in the plane in parallel to the substrate, with improved viewing angle but higher driving voltage needed and undesirably low transmittance.
FIG. 1 is a partial plan view of a disclosed liquid crystal display device, which discloses a liquid crystal display device with special electrode configuration, in which, for the sake of clarity, the second substrate is omitted; FIG. 2 is a partially sectional view along line A-A in FIG. 1. With reference to FIGS. 1 and 2, the liquid crystal display device comprises a first substrate 10, a second substrate 20 and a liquid crystal layer 30 interposed between the first substrate 10 and the second substrate 20. The first substrate 10 comprises a transparent substrate 101, and a plurality of scanning lines 1, a plurality of data lines 2, a plurality of common electrode lines 3 and thin film transistors 4 formed on the transparent substrate 101, the plurality of scanning lines 1 and the plurality of data lines 2 crosswise defining a plurality of pixel regions. As shown in FIG. 2, common electrodes 102a and pixel electrodes 102b are formed by a transparent conductive material layer which is directly formed on the transparent substrate 101, such as ITO (Indium Tin Oxide) layer, and common electrode lines 3 are formed by a first metal layer likewise which is directly formed on the transparent substrate 101. 103a, 103b, 103c, 103d in FIG. 2 are all formed by extension parts of common electrode lines 3 and electrically connected, and the common electrodes 102a are directly contacted with the extension parts of the common electrode lines 3 in some region resulting in electrical connection. A gate insulation layer 104 is located upon the ITO layer and the first metal layer directly formed on the transparent substrate, and the data lines 105a and 105b are located upon the gate insulation layer 104 and formed by a second metal layer. The data lines are covered by a passivation layer 106 upon, and a plurality of strip-like electrodes a, b, c, d, e, f, g, h formed by the ITO layer 107 are located upon the passivation layer 106, in which a, b, e, f, g, h are all common electrodes and electrically connected with the common electrode lines 3, and c, d are pixel electrodes and electrically connected with the pixel electrode 102b. As shown in FIG. 1, a drain electrode of thin film transistor 4 is electrically connected with the pixel electrodes c, d via a through hole C1, and meanwhile the pixel electrodes c, d are electrically connected with the pixel electrode 102b via a through hole C2. Two opposite sides of each data line both have a common electrode substantially in parallel to the data line so as to shield off the influence on the pixel electrodes from the data line signal during operation of the liquid crystal display device. As shown in FIGS. 1 and 2, two sides of the data line 105a have a common electrode a and a common electrode b, and two sides of the data line 105b have common electrodes g and h. In the direction perpendicular to the transparent substrate 101, the common electrodes a, b, g, h, in position, respectively correspond to the extension parts 103a, 103b, 103c, 103d of the common electrode lines, and the pixel electrodes c, d with a gap therebetween, in position, correspond to the common electrode 102a located underneath, to form an electrode group, and the common electrodes e, f with a gap therebetween, in position, correspond to the pixel electrode 102b located underneath, to form another electrode group. The pixel region shown in FIG. 1 only comprises these two electrode groups.
During operation of the liquid crystal display device, the liquid crystal molecules are affected by the horizontal electric field and the fringe field generated between the pixel electrodes and the common electrodes, so as to control the transmission of backlight to realize display of various gray scales. FIG. 2 only illustrates the situation when the voltage on the pixel electrodes is larger than that on the common electrodes, the direction of whose electric field lines is generally shown by the arrows in FIG. 2. The liquid crystal molecules located between the common electrode b and the pixel electrode c are affected by the horizontal electric field from the pixel electrode c to the common electrode b; the liquid crystal molecules located between the pixel electrode c and the pixel electrode d are affected by the fringe fields from the pixel electrode c to the common electrode 102a and from the pixel electrode d to the common electrode 102a; the liquid crystal molecules located between the pixel electrode d and the common electrode e are affected by the horizontal electric field from the pixel electrode d to common electrode e; the liquid crystal molecules located between the common electrode e and the common electrode f are affected by the fringe fields from the pixel electrode 102b to the common electrode e and from the pixel electrode 102b to the common electrode f; but as the potential between the common electrode f and the common electrode g are equal and there is no horizontal electric field generated, the liquid crystal molecules located between the common electrode f and the common electrode g (shown in dash line circular region in FIG. 2) are not affected by any electric field, and so that no matter the liquid crystal display device presents a light state or a dark state, the region is always in the dark state, that is, the dash line region L in FIG. 1 always presents the dark state, and therefore the electrode configuration of this liquid crystal display device would retard the enhancement of transmittance in pixel regions.